I used to do all kinds of eye experiments when I was younger.
I used to look staight at the sun with one eye fully open and hold it open looking directly at the sun and count off 10 or 15 seconds, but I found I could never keep both eyes open and look directly at the sun,, the signal was just too intense for my brain to handle. Never went blind from looking directly at the sun,,in fact I think it had some side benifits.